Sanding Pad For An Oscillatory Drive

ABSTRACT

A sanding pad is disclosed having a socket for connection to a drive shaft of an oscillatory drive, wherein the socket is configured for positive connection to the drive shaft of the oscillatory drive, wherein the socket is connected to a support element, and a cushion element of flexible material, on which a sanding surface is formed, is mounted on the support element, wherein the sanding pad has a rim area, a socket area, which surrounds the socket, and an intermediate area between the rim area and the socket area, and wherein the rim area is materially reinforced relative to the intermediate area.

CROSSREFERENCES TO RELATED APPLICATIONS

This application claims priority from German patent application serial number 10 2013 106 546.5, filed on Jun. 24, 2013. The entire contents of this priority application is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to a sanding pad having a socket for connection to a drive shaft of an oscillatory drive, wherein the socket is designed for connection for conjoint rotation to the drive shaft of the oscillatory drive, wherein the socket is connected to a support element, and a cushion element of flexible material, on which a sanding surface is formed, is mounted on the support element, wherein the sanding pad has a rim area, a socket area, which surrounds the socket, and an intermediate area between the rim area and the socket area.

A sanding pad of this kind is known from EP 2 218 546 A2.

The known sanding pad is designed for operation with an oscillatory drive, the working spindle of which is driven at high frequency and with a small swivel angle about the longitudinal axis thereof. It is thereby possible to achieve a particularly good sanding result, especially when triangular sanding tools with rounded outer edges are used. In this way, it is namely also possible to enable sanding along the longitudinal edges and the corners. Moreover, it is now the intention to use this sanding pad in a round embodiment also for surface sanding.

For this purpose, the quotient of the working surface of the tool (given in square millimeters) and of the rated power consumption of the drive motor (given in watts) is at least 35 mm²/W. Furthermore, the quotient of the working surface of the tool (given in mm²) and of the total weight of the oscillatory tool (given in grams, without a tool) is at least 5.5 mm²/g.

Here, the enlarged working surface of the sanding pad is to be combined with various measures for reducing the inertia of the sanding pad mounted on the drive shaft. The sanding pad has a socket made of steel, on which a support element made, for example, from an aluminum alloy is secured. In this arrangement, the support element has a larger area than the cushion element of flexible material mounted thereon and preferably extends over the entire diameter of the tool. The support element is used for mounting and supporting the cushion element, which is adhesively bonded to the support element over the full area. The cushion element is composed of a very flexible material, e.g. a polyurethane.

Although good stability of the sanding pad is ensured with a construction of this kind, the sanding pad still has an excessive moment of inertia in the case of relatively large diameters or relatively large areas in the case of triangular embodiments. As a result, the oscillatory drive is subject to high stress, and this can lead to premature wear of the oscillatory drive, or there is a disadvantageous effect on the sanding result. On the other hand, it is not possible to select an arbitrarily high motive power of the oscillatory drive and a correspondingly robust construction of the transmission since, in this case, the weight is significantly increased, and this has a disadvantageous effect on the ergonomics.

SUMMARY OF THE INVENTION

In view of this, it is a first object of the invention to disclose a sanding pad having a small moment of inertia.

It is a second object of the invention to disclose a sanding pad having a long-lasting mechanical stability.

It is a third object of the invention to disclose a sanding pad having a good mechanical stability and a small moment of inertia at the same time.

In one aspect of the invention, these and other objects are achieved by a sanding pad comprising:

a socket being configured for connection to a drive shaft of an oscillatory drive for oscillation with said drive shaft about a longitudinal axis thereof;

a support element being connected to said socket;

a cushion element made of flexible material being mounted on said support element;

a sanding surface being formed on said cushion element;

a rim area delimiting said sanding pad;

a socket area surrounding said socket;

an intermediate area extending between said rim area and said socket area;

wherein said rim area around a circumference thereof is reinforced relative to said intermediate area.

The object of the invention is achieved in this way.

According to the invention, adequate strength is achieved in the area in which greater strength is necessary, namely in the outer area, where the greatest stress occurs, through increased use of material, while the other areas, in particular the intermediate area, can be embodied so as to be significantly weaker, thereby reducing the moment of inertia overall.

In a preferred development of the invention, the rim area has a greater material thickness than the intermediate area.

Although it is fundamentally also possible to achieve a higher strength in the rim area in some other way, e.g. by fiber reinforcement, a greater material thickness is preferably used in the rim area than in the intermediate area.

According to another embodiment of the invention, the rim area is designed with a peripheral wall, which completely surrounds the intermediate area.

Increased strength is also ensured by this means.

According to another embodiment of the invention, the socket is made of metal and is connected positively and/or materially to the support element, which is made of plastic.

By means of the embodiment of the socket from metal, preferably from steel, sufficient strength is ensured to prevent deflection of the socket, even in continuous operation. By means of a positive connection, which can be combined with a material connection as an advantageous option, reliable torque transmission is ensured. This can preferably be ensured by overmolding in the case of production by injection molding, thereby giving a particularly intimate bond.

According to another embodiment of the invention, the cushion element is made of a foam having a lower strength than the support element.

By means of this feature, a favorable sanding result is made possible, on the one hand, and a reduced weight of the cushion element is made possible, on the other hand, since a foam has a significantly lower weight than (normal) plastic (rigid plastic). The cushion element can be composed of a polyurethane foam, for example. The support element can be composed of a fiber-reinforced polyamide, for example.

According to another embodiment of the invention, the cushion element is connected materially to the support element.

In this way, an intimate bond between the cushion element and the support element is ensured. This can be ensured, for example, by molding on directly during production, in particular by the “two-component method”. According to this method, two plastics of different hardness are injected successively into an injection mold, and an intimate material bond is achieved by virtue of the fact that the second, softer component is injected onto the first, harder component while it is still partially in the unsolidified state.

According to another embodiment of the invention, the sanding surface defines a first surface level, wherein the intermediate area defines a second surface level and the rim area defines a third surface level, which is further away from the first surface level than the second surface level in the intermediate area.

In this way, a greater material thickness is ensured in the rim area than in the intermediate area, and hence increased strength.

According to another embodiment of the invention, the sanding pad tapers outwards at least partially in the intermediate area on a rear side facing away from the sanding surface.

This saves material, especially towards the outside, thereby reducing the moment of inertia. In particular, this taper is formed on the cushion element, with the result that adequate strength continues to be ensured by the support element.

According to another embodiment of the invention, the sanding pad defines at least one corner area, wherein the support element has, in the corner area, a wall which surrounds the corner area and has an increased slope as compared with the remainder of the wall.

Through an increased slope in the corner area, more material is applied to the support element in the corner area overall, resulting in increased strength in the corner area, which is subjected to particularly high stress.

According to another embodiment of the invention, the cushion element projects outwards from the support element in the rim area and, in the rim area, has alternate reinforcing ribs, between which there extend depressions.

In this way, material is saved in the rim area, leading to a weight saving in the rim area and thus to a reduced moment of inertia. An embodiment of this kind is preferably used with circular sanding pads, rectangular sanding pads, oval or elliptical sanding pads.

According to another embodiment of the invention, extraction openings, which can be coupled via extraction channels to an extraction hose on the oscillatory drive, are provided on the sanding surface.

In this way, sanding dust which forms during sanding can be sucked off immediately.

According to a development of this embodiment, an annular web, which projects in the direction of the oscillatory drive, which surrounds the extraction channels on the outside and to which a suction hood of the oscillatory drive can be coupled, is provided on the side facing away from the sanding surface.

In this way, favorable coupling of an extraction device on the oscillatory drive to the extraction channels on the sanding pad is ensured.

According to another embodiment of the invention, an annular web, which projects in the direction of the oscillatory drive and which delimits the intermediate area with respect to the socket area, is provided on the side facing away from the sanding surface.

In this way, a suction space, which is delimited by an outer annular web and an inner annular web and which can be coupled directly to an associated suction hood of the oscillatory drive, is formed above the space from which the extraction channels emerge.

According to another embodiment of the invention, the sanding surface has a gripping element for the releasable fastening of a sanding or polishing element, preferably by means of a hook and loop material.

This enables the sanding pad to be used over the long term while the sanding or polishing element can be replaced in a simple manner as required.

The object of the invention is furthermore achieved by a sanding machine having an oscillatory drive, and having a drive shaft which can be oscillatingly driven and on which a sanding pad of the type described above is mounted.

In this arrangement, the drive shaft can be oscillatingly driven about the longitudinal axis thereof, preferably at a frequency of 5,000 to 25,000 oscillations per minute and at a swivel angle of 2° to 10°, preferably ±2° to ±4°. Here, the swivel angle is taken to be the total swept angle and the figure of ±2° is taken to be a pivoting angle of 2° in each of the two directions from the point of reversal, corresponding to a swivel angle of 4°.

The oscillatory drive furthermore preferably has an extraction device having an extraction hood, which can be coupled to the extraction channels opening in the sanding surface.

In this way, effective extraction directly at the sanding surface is ensured.

It is self-evident that the features mentioned above and those that remain to be explained below can be used not only in the respectively indicated combination but also in other combinations or in isolation without exceeding the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention will emerge from the following description of preferred illustrative embodiments with reference to the drawing, wherein:

FIG. 1 shows a perspective view of a sanding machine having an oscillatory drive, whereon a sanding pad of triangular shape according to the invention is mounted;

FIG. 2 shows a perspective view of the sanding pad shown in FIG. 1 from a side facing away from the sanding surface;

FIG. 3 shows a perspective view of the sanding pad from the opposite side;

FIG. 4 shows a plan view of the sanding pad shown in FIG. 3 vertically from above;

FIG. 5 shows a section through the sanding pad shown in FIG. 4 along the line V-V;

FIG. 6 shows a perspective view of a sanding pad according to the invention in a circular embodiment;

FIG. 7 shows a perspective view of the sanding pad shown in FIG. 6 from the opposite side;

FIG. 8 shows a plan view of the sanding pad shown in FIG. 6 vertically from above;

FIG. 9 shows a section through the sanding pad shown in FIG. 8 along the line IX-IX; and

FIG. 10 shows a perspective view of a sanding machine in an embodiment modified as compared with that in FIG. 1, said machine having an extraction device.

DESCRIPTION OF PREFERRED EMBODIMENTS

A sanding machine according to the invention is illustrated in perspective in FIG. 1 and is denoted overall by the number 10. The sanding machine 10 has a fundamentally known oscillatory drive 12, having a drive shaft 16 which can be driven backward and forward in oscillation about the longitudinal axis 18 thereof, more specifically at a high frequency and with a small swivel angle. The oscillation frequency is preferably 8,000 to 12,000 rpm, preferably 9,000 to 10,000 rpm. A universal motor with a rated power of about 600 to 700 W is used for driving.

The swivel angle is between 2° and 10°, preferably ±3°. The oscillatory drive 12 has an elongate housing, which is designed to be gripped with one hand, wherein a switch for switching on and off can be seen on the top side and a clamping lever 14 for quick-clamp fastening of a sanding pad 20 on the drive shaft 16 can be seen in the region of the transmission head.

In the example illustrated, the sanding pad 20 is of triangular design with rounded side edges. As will be explained below, circular embodiments are also conceivable, as are also in principle other shapes, such as rectangular, elliptical, oval etc.

If a circular sanding pad is used, this is designed for a diameter of about 150 mm at a rated power of 600 to 700 W.

The more detailed construction of the sanding pad according to the invention will now be explained in greater detail with reference to FIGS. 2 to 9.

A sanding pad of triangular design with rounded side edges is illustrated in FIGS. 2 to 5, while a sanding pad of circular shape is illustrated in FIGS. 6 to 9.

According to FIGS. 2 to 5, the sanding pad 20 has a centrally arranged socket area 22, in which a socket 44 made of metal, preferably made of steel, is provided, which is designed for connection for conjoint rotation to the drive shaft 16 of the oscillatory drive 12.

As can be seen from FIG. 5, a spring lock washer 46, which serves to secure a locating pin (not shown), which is inserted through the socket 44 into the drive shaft 16 (designed as a hollow shaft) in the sanding pad 20 with its head recessed, is preferably arranged directly adjacent to the socket 44.

As can be seen from FIG. 5, the sanding pad 20 comprises three elements, namely the central socket 44, a support element 48 connected materially to the socket 44, and a cushion element 52, which is mounted on the support element 48 and on which a sanding surface 28 is formed. The sanding surface 28 is provided with a gripping element 58, which is preferably designed as a hook and loop material and on which a sanding or polishing element (not shown) can be fastened in a releasable manner.

The socket 44 is connected positively and materially to the support element 48, which is composed of a rigid plastic of high rigidity, e.g. of a fiber-reinforced polyamide. The socket 44 is preferably directly overmolded by the support element 48. The support element 48 extends outwards from the socket 44 into the rim area 26 in accordance with FIG. 2 and, at the outer end, has a projection 50, which projects into the cushion element 52. The cushion element 52 is composed of a flexible plastic, preferably a polyurethane foam, preferably with a density of about 300 kg/m3, and is connected positively and materially to the support element 48. The sanding surface 28 or mounting surface 58 for mounting the sanding or polishing element is formed on the cushion element 52. The cushion element 52 furthermore extends into the rim area 26 and forms the outer boundary of the sanding pad 20.

As can be seen particularly from FIGS. 2 and 4, the sanding pad 20 has, starting from the central socket area 22, two further areas, namely an intermediate area 24, which adjoins the socket area 22 and is delimited with respect to the socket area 22 by a projecting annular web 38 of the support element 48, and the rim area 26, which is delimited with respect to the socket area 22 by another, outer annular web 32 of the support element 48.

The intermediate area 24 is thus delimited with respect to the socket area 22 and the rim area 26 by the two annular webs 38 and 32 respectively. In the intermediate area 24 there are extraction channels 34, 36, which open into the sanding surface 28 shown in FIG. 3 and which open into the intermediate area 24 on the opposite side shown in FIG. 2.

An associated extraction hood 72 on the oscillatory drive 12 of the sanding machine 10 a (cf. FIG. 10) forms a seal with the two annular webs 32, 38 (labyrinth seal) when the sanding tool 20 is secured on the drive shaft 16, with the result that the intermediate area 24 defines an extraction zone via which extraction via an extraction channel 74 connected to the extraction hood 72 and via an extraction hose 76 connected thereto can take place directly at the sanding surface 28 if an oscillatory drive 12 as shown in FIG. 10, with an extraction device, is used.

In FIG. 1, on the other hand, the sanding machine 10 is shown without an extraction device.

According to FIG. 5, a first surface level 60 is defined by the sanding surface 28, while the intermediate area 24 defines a second surface level 62, and the outer rim area 26 defines a third surface level 64, which is further away from the first surface level 60 than the second surface level 62 in the intermediate area 24.

In other words, the sanding pad is designed with less material thickness in the intermediate area 24 than in the rim area 26. This design results in increased strength in the rim area 26, while material is saved in the intermediate area 24, which is subjected to less stress.

In the triangular corner areas 30 shown in FIGS. 2 and 4, the peripheral wall 54 formed by the cushion element 52 is furthermore made steeper, i.e. with a greater slope, than in the remaining wall areas 56, particularly in the area of the rounded side edges. This embodiment too leads to increased rigidity or strength in the corner areas 30.

As can be seen particularly from FIG. 2, the intermediate area 24 has a series of raised areas 40 on the side thereof facing away from the sanding surface 28, each of said raised areas being delimited with respect to one another by recessed areas 42. The raised areas 40 taper outwards in the direction of the outer annular web 32 (reduction in the material thickness in the axial direction). The recessed areas 42 each enclose an extraction channel 34 with a relatively small cross section and an extraction channel 36 with a relatively large cross section. Extraction channels 34 with a relatively small cross section likewise open into the raised portions 40, just in front of the annular web 32, at the outer ends of the raised areas 40.

By means of the taper of the raised portions 40 from the inner annular web 38 in the direction of the outer annular web 32 (reduction of the material thickness) and by means of the additional depressions in the recessed areas 42, material is saved, with the result that the moment of inertia of the sanding pad 20 is significantly reduced.

A modified embodiment of the sanding pad is shown in FIGS. 6 to 9 and is denoted overall by the number 20 a. Otherwise, corresponding reference numbers are used for corresponding parts. The significant difference with respect to the sanding pad 20 of the type described above consists in the circular embodiment of the sanding pad 20 a.

The foam of the cushion element 58 projects outwards beyond the outer annular web 32 which delimits the intermediate area 24 with respect to the rim area 26. A series of depressions 70 is formed in the overlap thus formed of the rim area 26, with the result that respective reinforcing ribs 68 remain in between. Overall, a significant reduction in material is made possible in the rim area 26 while maintaining adequate strength, and this likewise leads to a reduction in the moment of inertia.

In this embodiment too, raised areas 40 are furthermore formed in the intermediate area 24, each of said areas being delimited with respect to one another by recessed areas 42, into which the extraction channels 34 and 36 open.

Overall, a reduction in material is achieved by means of the greater material thickness in the rim area 26 and the reduced material thickness in the intermediate area 24 while maintaining adequate strength, and this leads to a reduced moment of inertia and thus to a lower load on the drive or allows sanding with a larger surface in comparison with the prior art. 

What is claimed is:
 1. A sanding pad comprising: a socket being configured for connection to a drive shaft of an oscillatory drive for oscillation with said drive shaft about a longitudinal axis thereof; a support element being connected to said socket; a cushion element made of flexible material being mounted on said support element; a sanding surface being formed on said cushion element; a rim area delimiting said sanding pad; a socket area surrounding said socket; and an intermediate area extending between said rim area and said socket area; wherein said rim area is reinforced relative to said intermediate area; wherein said sanding surface defines a first surface level; wherein said intermediate area defines a second surface level; and wherein said rim area defines a third surface level, which is further away from said first surface level than said second surface level in said intermediate area.
 2. The sanding pad of claim 1, wherein said rim area has a greater material thickness than said intermediate area.
 3. The sanding pad of claim 1, wherein said rim area comprises a peripheral wall completely surrounding said intermediate area.
 4. The sanding pad of claim 1, wherein said socket is made of metal, wherein said support element is made of plastic, and wherein said support element is fixed directly to said socket.
 5. The sanding pad of claim 4, wherein said socket is fixed positively to said socket.
 6. The sanding pad of claim 1, wherein said cushion element is made of a foam having a lower strength than said support element.
 7. The sanding pad of claim 1, wherein said cushion element is molded to said support element.
 8. The sanding pad of claim 1, wherein said sanding pad tapers outwards at least partially in said intermediate area on a rear side facing away from said sanding surface.
 9. The sanding pad of claim 1, wherein said sanding pad comprises at least one corner area, and wherein said support element comprises a wall surrounding said corner area and said rim area, said wall having an increased slope in said corner area relative to said longitudinal axis as compared with a remainder of said wall outside said corner area.
 10. The sanding pad of claim 1, wherein said cushion element projects outwards from said support element within said rim area, and wherein said rim area further comprises reinforcing ribs arranged around a circumference of said rim area, wherein a depression extends between each pair of adjacent reinforcing ribs.
 11. The sanding pad of claim 1, wherein said sanding surface further comprises extraction openings being configured for coupling to an extraction means on said oscillatory drive.
 12. The sanding pad of claim 11, further comprising a first annular web arranged on a side facing away from said sanding surface, said annular web projecting in a direction of said oscillatory drive, surrounding said extraction channels on the outside, and being configured for coupling to an extraction hood of said oscillatory drive.
 13. The sanding pad of claim 12, further comprising a second annular web arranged on a side facing away from said sanding surface, projecting in the direction of said oscillatory drive and delimiting said intermediate area with respect to said socket area.
 14. The sanding pad of claim 1, wherein said sanding surface comprises a gripping element configured for releasable fastening of a sanding or polishing element.
 15. The sanding pad of claim 14, wherein said gripping element is configured as a hook and loop material.
 16. A sanding pad comprising: a socket being configured for connection to a drive shaft of an oscillatory drive for oscillation with said drive shaft about a longitudinal axis thereof; a support element being connected to said socket; a cushion element made of flexible material being mounted on said support element; a sanding surface being formed on said cushion element; a rim area delimiting said sanding pad; a socket area surrounding said socket; an intermediate area extending between said rim area and said socket area; wherein said rim area around a circumference thereof is reinforced relative to said intermediate area; and wherein said cushion element projects outwards from said support element within said rim area, and wherein said rim area further comprises reinforcing ribs arranged around a circumference of said rim area, wherein a depression extends between each pair of adjacent reinforcing ribs.
 17. A sanding pad comprising: a socket being configured for connection to a drive shaft of an oscillatory drive for oscillation with said drive shaft about a longitudinal axis thereof; a support element being connected to said socket; a cushion element made of flexible material being mounted on said support element; a sanding surface being formed on said cushion element; a rim area delimiting said sanding pad; a socket area surrounding said socket; an intermediate area extending between said rim area and said socket area; wherein said rim area around a circumference thereof is reinforced relative to said intermediate area.
 18. A sanding machine comprising an oscillatory drive having a drive shaft oscillatingly driven about a longitudinal axis thereof, and further comprising a sanding pad attached to an outer end of said drive shaft, said sanding pad comprising: a socket being configured for connection to a drive shaft of an oscillatory drive for oscillation with said drive shaft about a longitudinal axis thereof; a support element being connected to said socket; a cushion element made of flexible material being mounted on said support element; a sanding surface being formed on said cushion element; a rim area delimiting said sanding pad; a socket area surrounding said socket; an intermediate area extending between said rim area and said socket area; wherein said rim area around a circumference thereof is reinforced relative to said intermediate area.
 19. The sanding machine of claim 18, wherein said oscillatory drive further comprises an extraction hood being configured for coupling to said sanding pad.
 20. The sanding machine of claim 18, wherein said sanding surface defines a first surface level, in that said intermediate area defines a second surface level and in that said rim area defines a third surface level, which is further away from said first surface level than said second surface level in said intermediate area. 